The Thermo-Economic Potential of ORC-Based Pumped-Thermal Electricity Storage: Insights from the Integrated Design of Processes and Working Fluids

Higher shares of renewable energy increase the need for electricity storage. A promising storage technology is Pumped-Thermal Electricity Storage (PTES): PTES systems transform electricity into heat using a heat pump (HP) and reconvert the heat into electricity using a heat engine. Since both heat pumps and heat engines require working fluids, maximum performance requires the optimal combination of PTES process and working fluids. In this work, we analyze the thermo-economic potential of an ORC-based PTES system by simultaneously designing both the PTES process and the working fluids used in the heat pump and the ORC. To rigorously explore the molecular design space, we employ the 1-stage Continuous-Molecular Targeting - Computer-Aided Molecular Design method. Detailed models for costing and sizing of the equipment allow for a thermo-economic design of the PTES. The computer-aided molecular design formulation integrates the working fluids as degrees of freedom into the process optimization. For the investigated ORC-based PTES system with an input power of 60 MW for daily storage, the optimal process and working fluids minimize the specific investment cost to SIC=929 € kWh−1out. The analysis of cost drivers shows that with decreasing compressor cost, the investigated ORC-based PTES system could become a competitive storage technology.ISSN:2194-4296ISSN:2194-428